Little is left to the West Fertilizer plant as seen in an aerial view of the plant on Thursday, April 18, 2013, in West, Texas.

Little is left to the West Fertilizer plant as seen in an aerial view of the plant on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Little is left to the West Fertilizer plant as seen in an aerial... Photo-4493628.60613 - Houston Chronicle

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Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas. The plnat is at center bottom of the photo.

Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas. The plnat is at center bottom of the photo.

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant is seen in... Photo-4493622.60613 - Houston Chronicle

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Homes damaged from the explosion of the West Fertilizer plant are seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Homes damaged from the explosion of the West Fertilizer plant are seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Homes damaged from the explosion of the West Fertilizer plant are... Photo-4493405.60613 - Houston Chronicle

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Little is left to the West Fertilizer plant as seen in an aerial view of the plant on Thursday, April 18, 2013, in West, Texas.

Little is left to the West Fertilizer plant as seen in an aerial view of the plant on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Little is left to the West Fertilizer plant as seen in an aerial... Photo-4493629.60613 - Houston Chronicle

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Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas. The plant is a the left of the photo. An apartment complex is at center. A nursing home is at top right. less

Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas. The plant is a the left of the photo. An apartment complex is at ... more

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant is seen in... Photo-4493624.60613 - Houston Chronicle

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Little is left to the West Fertilizer plant as seen in an aerial view of the plant on Thursday, April 18, 2013, in West, Texas.

Little is left to the West Fertilizer plant as seen in an aerial view of the plant on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Little is left to the West Fertilizer plant as seen in an aerial... Photo-4493626.60613 - Houston Chronicle

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Damage from the explosion of the West Fertilizer plant, at right, is seen in an aerial view on Thursday, April 18, 2013, in West, Texas. A nursing home is at left. An apartment complex is at center.

Damage from the explosion of the West Fertilizer plant, at right, is seen in an aerial view on Thursday, April 18, 2013, in West, Texas. A nursing home is at left. An apartment complex is at center.

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant, at right,... Photo-4493407.60613 - Houston Chronicle

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A law enforcement helicopter flies over a nursing home damaged from the explosion of the West Fertilizer plant on Thursday, April 18, 2013, in West, Texas.

A law enforcement helicopter flies over a nursing home damaged from the explosion of the West Fertilizer plant on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

A law enforcement helicopter flies over a nursing home damaged from... Photo-4493412.60613 - Houston Chronicle

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Damage to the middle school and school administration buildings from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Damage to the middle school and school administration buildings from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Damage to the middle school and school administration buildings... Photo-4493611.60613 - Houston Chronicle

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Damage from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Damage from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant is seen in... Photo-4493630.60613 - Houston Chronicle

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Damage to private homes from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Damage to private homes from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Damage to private homes from the explosion of the West Fertilizer... Photo-4493408.60613 - Houston Chronicle

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Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas.

Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant is seen in... Photo-4493631.60613 - Houston Chronicle

Image 14 of 20

A law enforcement helicopter flies over homes damaged from the explosion of the West Fertilizer plant on Thursday, April 18, 2013, in West, Texas.

A law enforcement helicopter flies over homes damaged from the explosion of the West Fertilizer plant on Thursday, April 18, 2013, in West, Texas.

Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas. The plant is a the bottom of the photo. An apartment complex is at center. A nursing home is at top. less

Damage from the explosion of the West Fertilizer plant is seen in an aerial view of the city on Thursday, April 18, 2013, in West, Texas. The plant is a the bottom of the photo. An apartment complex is at ... more

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant is seen in... Photo-4493633.60613 - Houston Chronicle

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A nursing home damaged from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

A nursing home damaged from the explosion of the West Fertilizer plant is seen in an aerial view on Thursday, April 18, 2013, in West, Texas.

Photo: Smiley N. Pool, Houston Chronicle

A nursing home damaged from the explosion of the West Fertilizer... Photo-4493619.60613 - Houston Chronicle

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Damage from the explosion of the West Fertilizer plant, at top, is seen in an aerial view on Thursday, April 18, 2013, in West, Texas. A nursing home is at bottom. An apartment complex is at center.

Damage from the explosion of the West Fertilizer plant, at top, is seen in an aerial view on Thursday, April 18, 2013, in West, Texas. A nursing home is at bottom. An apartment complex is at center.

Photo: Smiley N. Pool, Houston Chronicle

Damage from the explosion of the West Fertilizer plant, at top, is... Photo-4493409.60613 - Houston Chronicle

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Law enforcement and rescue personnel search the damage to an apartment complex from the explosion of the West Fertilizer plant on Thursday, April 18, 2013, in West, Texas.

Law enforcement and rescue personnel search the damage to an apartment complex from the explosion of the West Fertilizer plant on Thursday, April 18, 2013, in West, Texas.

This video image provided by WFAA-TV shows injured people being treated on the flood-lit the high school football field turned into a staging area after the blast in West Texas Wednesday April 17, 2013.

This video image provided by WFAA-TV shows injured people being treated on the flood-lit the high school football field turned into a staging area after the blast in West Texas Wednesday April 17, 2013.